Cool Science: Silver Chloride Photochemistry

Cool Science: Silver Chloride Photochemistry


Greetings fellow nerds. Today we’re going to use the silver nitrate made in a previous video to do a simple photography experiment. First you’ll need about one gram of silver nitrate and half a gram of table salt. Add enough water to both to completely dissolve them. Once they are both dissolved, add the salt solution to the silver nitrate solution. It will instantly form a dense precipitate of silver chloride. Give it a good shake to thoroughly mix the chemicals. Then let it stand for five minutes to settle down to the bottom. Then pour off the excess liquid. Now you have a solid powder of silver chloride. Get a piece of filter paper or paper towel and dump out the silver chloride onto it. Then carefully spread it out and pack it down into a thin but solid layer. Dry off the powder as much as you can with paper towel but don’t break up the silver chloride layer. Now let the silver chloride dry in a dark place. When it’s dry, take it out, and then place ontop of it, a template of something you want imprinted onto the silver chloride. Then place a sheet of glass over the template to hold it flat and steady. When you’re ready, shine a very strong light onto the silver chloride. Over the course of ten minutes, the silver chloride will decompose under the light to form a negative image of what was placed over it. Modern photography is much better and faster but this experiment shows you the basic idea. After ten minutes, remove the glass and the template. And now you have a negative photograph of the template. Pretty cool eh? Thanks for watching another NurdRage science video. Please Subscribe, Rate and Comment.

100 Comments

  1. could you prepare the AgCl ahead of time so that it is already dry? Would you spread a thin layer onto a solid support and expsose as demonstrated? and I assume store it away from light.

  2. I see you're backed-up with questions here lol. But can te AgCl be recycled, so that darkened powder can be re-lightened? Preferably without requiring chlorine gas to do it haha.

    Great video though, thanks for sharing!

  3. With fixer.

    You can make your own universal fixer from sodium thiosulphate (found at pool supply stores) or just use fixer.

  4. You can mix it with food gelatin found at stores to make an emulsion layer you can spread over something rather than straight powder.

  5. Yes, with a rehalogenating bleach, for example a solution of potassium ferricyanide and sodium bromide, or in this case you probably want sodium chloride – which should work – I think.

  6. we were just learning about this in class! i had a hard time getting everything down, but this video gives me a good idea.thanks!!

  7. if you want to store the silver chloride for long periods of time without fear of photodecomposition, cleaned out amber glass A1 steak sauce bottles are GREAT!

  8. @NurdRage Why not soak the filter at first with AgNO3 and then after drying apply NaCl solution? I guess, then the Ag- ions should be incorporated in the paper, right?

  9. @JibbyDee The photons excite the compound to a state that allows "bond cleavage":
    AgCl –> Ag+ and Cl-. Think of it as an activation energy of the HOMO electrons (commonly binding molecular orbital) to the LUMO (commonly antibinding). In this case, the HOMO contributes electrons to silver and the LUMO does not. The unstable ions inevitably react. When they react in the following manner, then the reaction is irreversible: Ag+ + AgCl + Cl- –> Ag2(s) + Cl2(g).

  10. Another great video thanks. I am trying to find the correct way of making a 10% silver nitrate solution to make wet plate collodion photographic plates. I know it involves distilled or deionized water, nitric acid and silver nitrate but can only find ready made solutions with no instructions on how to make it myself. Any ideas?
    Cheers
    Richard

  11. Nothing more than you have seen, the silver nitrate is orthochromatic and as far as i know only sensitive to blue and infra-red but translates it as differing shades of white through to black.

  12. If my silver nitrate is contaminated with copper (blue liquid) and very strong, do you think it's better to add a liter of water or so before adding salt?

  13. Thanks so much for the video 🙂 I had a hard time understanding the chemistry behind photography in my book. This video helped a lot.

  14. Nice experiment but huge waste of expensive Silver Nitrate. add mix to the warm gelatin and stir for 15 minutes in subdued light. Coat watercolor paper with that Silver-gelatin emulsion, develop with photo chemicals ( dev, stop,fix).

  15. I'm interested in photochromism and am curious if you could replicate the redox of copper oxide and silver chloride used in transition glass; without the glass. Just have a powder that goes from black to clear?

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